Water as brine often exists in the same formation as oil or gas. The development of oil- or gas-containing reservoirs simultaneously results in the production of water in such amount that it raises serious problems: formation of deposits at the vicinity of the well or in the tubing, increase of the corrosion of metal parts, formation of emulsions with oil which are very difficult to break. When offshore drillings are concerned, the water production in large amount raises, in addition, problems of storage and of discharge.
Many methods destined to reduce the water inflows in the production wells have been proposed and tested on the field. They generally consist of placing in the formation, at the water and oil or gas interface, a tight barrier consisting for example of cements, resins, suspensions of solid particles or of paraffins. These clogging agents have the disadvantage of blocking the oil or gas as well as the water inflow, particularly when the water inflow results from a water coning phenomenon.
More recently, it has been proposed to use hydrolyzed polyacrylamides. However, this type of polymer is efficient mainly against inflows of water of low salt content and has a decreasing activity with water of increased salt content. Moreover, by temperature effect, these polyacrylamides progressively hydrolyze and thus precipitate in the presence of plurivalent ions.
Another technique for preventing water inflows in producing wells uses the property of various polymers, poly-acrylamides and xanthan gums, to cross-link by action of salts of trivalent ions such as chromium and aluminum ions. It has been observed that this cross-linking to more or less compact gels results effectively in the stopping or reduction of the water inflow, but also affects to a large extent the oil or gas production.